#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 65;

int n, m;
char a[N][N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n;
  rep(i, 1, n) rep(j, 1, n) {
    int x = min(i, n + 1 - i);
    int y = min(j, n + 1 - j);
    int z = min(x, y);
    a[i][j] = (z & 1) ? '#' : '.';
  }
  rep(i, 1, n) {
    rep(j, 1, n) cout << a[i][j];
    cout << endl;
  }
  return 0;
}